Field of the Invention
The disclosed concept relates to an arc extinguishing contact assembly for a circuit breaker assembly and, more particularly to an arc extinguishing contact assembly for a circuit breaker assembly that utilizes a number of displaced pressure zones adjacent a conductive element of the contact assembly to extinguish an arc.
Background Information
Air, or gas, circuit breakers include a contact assembly disposed in a chamber. The contact assembly includes both main contacts and arc contacts. That is, there are a number of main fixed contacts and a number of main movable contacts wherein each movable contact has an associated fixed contact. The associated contacts are also identified herein as a “pair of main contacts” or a “set of main contacts.” Each movable main contact moves between an open, first position, wherein the movable main contact is spaced from and not in electrical communication with the associated fixed main contact, and, a closed, second position, wherein the movable main contact is directly coupled to and in electrical communication with the associated main fixed contact.
Similarly, each set of arc contacts includes a fixed arc contact and a movable arc contact. As with the main contacts, the arc contacts are disposed in pairs with the movable arc contact moveable between an open, first position, wherein the movable arc contact is spaced from and not in electrical communication with the associated fixed arc contact, and, a closed, second position, wherein the movable arc contact is directly coupled to and in electrical communication with the associated arc fixed contact. The arc contacts are structured to be directly coupled to each other before the main contacts when the movable contact assembly is moving into the closed position, and, are structured to decouple after the associated main contacts when the movable contact assembly is moving into the open position. When the movable arc contact is a specific distance from the fixed arc contact, when moving either toward or away therefrom, an arc forms between the movable arc contact and the fixed arc contact. The arc causes a number of problems including, but not limited to, degradation of the contacts. That is, the arc scorches the contacts. Further, the arc generates hot and hazardous gases with extreme pressure. The eroded/degraded contacts have an oxide layer on the contacts that increases the contact resistance between the main contacts which further increases the contact temperature due to ohmic heating and thus, limits the current carrying capability of the circuit breaker. Further, degradation makes circuit breaker inoperative and useless.
It is known to use directed fluid (gas) flow to extinguish, or assist in extinguishing, an arc. That is, the fluid passes through a fluid control port adjacent to the arc contacts and assists in dissipating the arc. In this configuration, the fluid control port may be one of the elements that is scorched by the arc. The fluid control port, which may be specifically shaped, and therefore is more expensive than other components, degrades over time and needs replaced. In this configuration, the arc suppression system is known as a “puffer,” and the circuit breaker is known as a “puffer breaker.” In a puffer breaker, generally, the arcing contacts are changed regularly and commonly identified as “consumables.” Replacement of the consumables usually happens in the high voltage circuit breakers where the arcing damage to the arcing contacts occurs frequently. Medium and low voltage circuit breakers also suffer degradation, but typically at a slower rate.
The fluid control ports, i.e., the fluid passages that direct the suppression fluid, are generally formed in one of two ways: 1) machined ports in the arc extinguishing components, or, 2) formed in-between the relative positions of the moving components. It is possible that both types of fluid passages are damaged due to arc scorching.
Further, the contact assemblies generally include large, conductive contact elements. These elements, typically made from copper, are expensive and difficult to replace. The inadequate design of copper alloy contacts put extra responsibility on the arc quenching media for the arc interruption. A puffer breaker, typically, uses Sulfur Hexafluoride (SF6) gas as an arc quenching media. SF6 gas has higher global-warming potential value, may be harmful to humans, and otherwise degrades the environment. If the air is used as a quenching media in a puffer breaker, the size of the circuit breaker is larger than that of a SF6 puffer breaker because of relatively lower arc quenching capability of air.
There is, therefore, a need for an arc extinguishing contact assembly for a circuit breaker assembly that overcomes these disadvantages. There is, for example, a need for an arc extinguishing contact assembly for a circuit breaker assembly wherein the local voltage of the arc is reduced by dividing the arc in multiple arcs and thereby limiting the deleterious effects of the arc. There is a further need for an arc extinguishing contact assembly for a circuit breaker assembly that reduced the contact erosion. There is a further need for an arc extinguishing contact assembly for a circuit breaker assembly, such as but not limited to a fluid control port, including a swirling gas passage, that is spaced from the contact assembly. There is a further need for an arc extinguishing contact assembly for a circuit breaker assembly including different emission materials positioned in the arcing contacts whereby the arc is controlled.